Explosive compositions with reduced fume

ABSTRACT

Explosive compositions including coated urea and an explosive including ammonium nitrate and fuel oil are provided. The explosive compositions can generate reduced levels of nitrogen oxide upon detonation. Methods of loading a blasthole with the explosive compositions and methods of reducing post-blast nitrogen oxide are also provided.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to Australian Provisional Patent Application No. 2019900023, entitled “EXPLOSIVE COMPOSITIONS WITH REDUCED FUME,” filed Jan. 4, 2019, the contents of which are hereby incorporated herein by reference in their entirety.

TECHNICAL FIELD

The present disclosure relates generally to explosives. More specifically, the present disclosure relates to explosive compositions with reduced fume.

DETAILED DESCRIPTION

Explosive compositions that generate reduced levels of nitrogen oxide upon detonation are disclosed herein, along with related methods. Explosive compositions are commonly used in the mining, quarrying, and excavation industries for breaking rocks and ore. Generally, a hole, referred to as a “blasthole,” is drilled into a surface, such as the ground. An explosive composition is placed in the blasthole and then subsequently detonated.

In some embodiments, the explosive composition includes i) an explosive including ammonium nitrate and fuel oil (ANFO) and ii) coated urea. In certain embodiments, the explosive is an explosive blend and further comprises an emulsion.

“Emulsion” as used herein encompasses both unsensitized emulsion matrix and emulsion that has been sensitized into emulsion explosive. For example, the unsensitized emulsion matrix may be transportable as a UN Class 5.1 oxidizer. Emulsion explosives include a sufficient amount of sensitizing agent to render the emulsion detonable with standard detonators. The emulsion may be sensitized at the blast site or even in the blasthole. In some embodiments, the sensitizing agent is a chemical gassing agent. In some embodiments, the sensitizing agent includes hollow microspheres or other solid gas-entraining agents. In some embodiments, the sensitizing agent is gas bubbles that have been mechanically introduced into the emulsion. The introduction of gas bubbles into the emulsion may decrease the density of the emulsion that is delivered to the blasthole.

Provided herein are explosive compositions that may have an energy similar to standard heavy ANFO and/or gassed emulsion blend products. The explosive compositions can include coated urea, which may reduce the energy of the explosive composition by the incorporation percentage of the coated urea. The use of coated urea, as described herein, can allow for the use of prill in blends in ground that may be prone to generating a significant level of fume. The majority of fume generally arises from the incomplete reaction of ammonium nitrate contained in the prill when blasting in certain ground types (e.g., ground that is cracked and/or fissured, ground with relatively high water levels, and/or ground comprising certain types of clay). Without being bound by any one particular theory, it is hypothesized that the presence of oxides of nitrogen (NOx) scavenging compounds formed from thermal decomposition of the coated urea may lead to a lower level of fume generation. The explosive compositions provided herein may be useful for the blasting of ground that requires a relatively high level of “heave” energy (i.e., that found in blasting coal overburden). Heave energy can be provided by the presence of ammonium nitrate prill; however, it is the ammonium nitrate prill that can also generate post-blast NOx fume. Inclusion of coated urea in the explosive composition can reduce the level of fume generated due to the formation of scavenging chemical species during and/or immediately after a detonation reaction.

In some other configurations, an explosive composition may include ammonium nitrate, uncoated urea, and emulsion. It has been observed, that as the amount of ammonium nitrate relative to emulsion is increased in such an explosive composition, liquefaction of the ammonium nitrate and uncoated urea can occur at ambient temperatures, which can result in column slumping (e.g., in a blasthole). For example, as the critical relative humidity of the key solids is relatively low in combination, decreased levels of emulsion and increased ammonium nitrate to urea ratios can create a mixture wherein liquefaction and slumping may occur.

The explosive compositions provided herein include coated urea as described in further detail below. Liquefaction and column slumping can be avoided with the explosive compositions disclosed herein. In some embodiments, the explosive composition may include ammonium nitrate, fuel oil, and coated urea without emulsion or with only minimal amounts of emulsion (e.g., 10-50% emulsion or even only 10-20% emulsion). When the explosive composition includes emulsion, the emulsion may be sensitized or unsensitized. Furthermore, the explosive composition may exhibit reduced post-blast nitrogen oxide production and increased energy relative to other low-fume products.

Explosive compositions that generate reduced levels of nitrogen oxide upon detonation are disclosed herein. Methods of loading a blast hole with an explosive composition and methods of reducing post-blast nitrogen oxide are also disclosed herein. It will be readily understood that the components of the embodiments as generally described below could be arranged and designed in a wide variety of different configurations. Thus, the following more detailed description of various embodiments, as described below, is not intended to limit the scope of the disclosure, but is merely representative of various embodiments.

An aspect of the disclosure is directed to explosive compositions. The explosive composition can include i) an explosive including ammonium nitrate and fuel oil and ii) coated urea. In some embodiments, the ratio of the explosive to the coated urea may be from about 1:1 to about 3:1, about 1.25:1 to about 2.75:1, about 1.5:1 to about 2.5:1, or about 1.75:1 to about 2.25:1.

Examples of fuel oil include, but are not limited to, liquid fuels such as diesel fuel, kerosene, and combinations thereof. Any fuel oil known in the art and compatible with ammonium nitrate and coated urea may be used.

The explosive composition may include from about 0.5 weight percent (wt %) to about 30 wt %, about 1 wt % to about 20 wt %, about 5 wt % to about 20 wt %, or less than about 5 wt % coated urea. In some embodiments, the coated urea may be in the form of prills or granules. Moreover, the coated urea may include a coating that inhibits, prevents, or resists the passage of water (e.g., a water resistant coating). The water resistant coating may be selected from at least one of a polymer, a wax, a stearate, a silicone polymer, a hydrophobic clay, a hydrophobic silica, a hydrophobic and particulate solid, a dimer acid, an oligomeric acid, and/or a combination thereof. For example, the water resistant coating may be a polymer selected from at least one of polyethylene terephthalate (PET), low-density polyethylene (LDPE), high-density polyethylene (HDPE), low-density polypropylene (LDPP), high-density polypropylene (HDPP), a polyamide, a polyester, polylactic acid, acrylonitrile butadiene styrene (ABS), polystyrene, and/or a combination thereof. Other suitable water resistant coatings are also within the scope of this disclosure. The coating may reduce or slow down dissolution of the urea (e.g., the urea prill or granule) by water. Accordingly, the coating may be hydrophobic or significantly hydrophobic.

In some embodiments, the explosive composition may further include an emulsion. For example, the explosive composition may include from about 10 wt % to about 60 wt %, about 20 wt % to about 50 wt %, or about 30 wt % to about 40 wt % emulsion. The explosive composition is not particularly limited in the amount of emulsion that can be incorporated into the blend; however, one of the advantages of the explosive composition is that low emulsion blends are possible without liquefaction of the ammonium nitrate and urea. Any emulsion known in the art and compatible with the ammonium nitrate, the fuel oil, and the coated urea may be used.

The explosive composition may be water resistant. The explosive composition may be resistant to liquefaction in humid and warm conditions. The critical relative humidity (CRH) for an ammonium nitrate-urea blend is 18.1% at 30° C.; accordingly the blends can adsorb moisture readily. The presence of emulsion at low levels (e.g., from about 0 wt % to about 60 wt %) can add water to the system due to diffusion out from the oxidizer and can decrease the available sleep time due to the mutual dissolution of ammonium nitrate and uncoated urea. At higher emulsion levels, the ammonium nitrate emulsion (ANE) can coat the prill and slow down the absorption of moisture. As such, high emulsion blends (e.g., greater than about 60 wt % emulsion) may not require coated urea for usable sleep times. However, the coating can allow for significantly longer sleep times. The color of the coating may also add to the visual appeal of the blend.

In various embodiments, the explosive composition may be resistant to liquefaction. For example, upon disposition of the explosive composition in a blasthole, the explosive composition may avoid or be resistant to slumping. Furthermore, upon detonation of the explosive composition, production of post-blast nitrogen oxide may be reduced. For example, in comparison to explosive agents lacking urea (i.e., control explosive agents) the explosive compositions as provided herein can exhibit lowered or reduced amounts or levels of post-blast nitrogen oxide.

Another aspect of the disclosure is directed to methods of loading a blasthole with an explosive composition. The method may include i) mixing an explosive comprising ammonium nitrate and fuel oil with coated urea to form an explosive composition and ii) delivering the explosive composition to the blasthole. The method may further include adding an emulsion to the explosive composition prior to delivering the explosive composition to the blasthole. With a mobile processing unit (MPU) having three bins (i.e., a standard MPU), the ammonium nitrate and the coated urea may be combined together using a “grouper” mixer (i.e., two augers are combined into one stream and the mixed product is augered into the bin). With an MPU having four bins (i.e., a quad MPU), the coated urea may be loaded into a “bulking agent” bin, which is then mixed with ammonium nitrate and fuel oil on the MPU.

Any combination of the components and the amounts or concentrations thereof described in reference to the explosive compositions as provided above may also be incorporated into the methods of loading a blasthole with the explosive compositions. Furthermore, any of the characteristics or measurements of the explosive compositions as provided above (e.g., water resistance and liquefaction resistance) may also be applicable to the explosive compositions prepared by the disclosed methods.

In some embodiments, the method may include detonating the explosive composition in the blasthole. Upon detonation of the explosive composition, the production of post-blast nitrogen oxide may be lowered or reduced relative to the amount of post-blast nitrogen oxide generated by a control explosive agent as described above.

Another aspect of the disclosure is directed to methods of reducing post-blast nitrogen oxide. The method may include i) mixing an explosive including ammonium nitrate and fuel oil with coated urea to form an explosive composition and ii) delivering the explosive composition to a blasthole. The method may further include adding an emulsion to the explosive composition prior to delivering the explosive composition to the blasthole.

Any combination of the components and the amounts or concentrations thereof described in reference to the explosive compositions as provided above may also be incorporated into the methods of reducing post-blast nitrogen oxide. Furthermore, any of the characteristics or measurements of the explosive compositions as provided above may also be applicable to the explosive compositions used in the methods of reducing post-blast nitrogen oxide.

In some embodiments, the method may include detonating the explosive composition in the blasthole. Upon detonation of the explosive composition, the production of post-blast nitrogen oxide may be lowered or reduced relative to the amount of post-blast nitrogen oxide generated by a control explosive agent as described above.

EXAMPLES

The following examples are illustrative of disclosed methods and compositions. In light of this disclosure, those of skill in the art will recognize that variations of these examples and other examples of the disclosed methods and compositions would be possible without undue experimentation.

Example 1

Chemically sensitized blends of emulsion (DYNO NOBEL®, TITAN® 9000), ammonium nitrate fuel oil (ANFO), and coated urea bulking agent were tested. It was observed that a ratio of 3:1 ANFO to coated urea appeared to be sufficient to reduce post-blast nitrogen oxide generation.

In ground with proven high fume potential, the chemically sensitized blend of emulsion, ANFO, and coated urea exhibited a very small level of orange fume or dust arising upon detonation.

Example 2

Blends including 30 wt %, 40 wt %, and 50 wt % emulsion with an initial ANFO:coated urea ratio of 3:1 were investigated for their physical properties with regards to explosives performance. Coated urea concentrations ranging from 5 wt % to 20 wt % were also investigated to establish upper and lower limits for such blends. Product stability, water resistance, and compression of the blends were assessed and no significant differences to standard/control were observed. In comparison, severe liquefaction of the solid components was observed with the use of uncoated urea. Accordingly, the coating effectively made the urea component inert for the testing.

Without further elaboration, it is believed that one skilled in the art can use the preceding description to utilize the present disclosure to its fullest extent. The examples and embodiments disclosed herein are to be construed as merely illustrative and exemplary and not a limitation of the scope of the present disclosure in any way.

Any methods disclosed herein include one or more steps or actions for performing the described method. The method steps and/or actions may be interchanged with one another. In other words, unless a specific order of steps or actions is required for proper operation of the embodiment, the order and/or use of specific steps and/or actions may be modified. Moreover, sub-routines or only a portion of a method described herein may be a separate method within the scope of this disclosure. Stated otherwise, some methods may include only a portion of the steps described in a more detailed method.

Reference throughout this specification to “an embodiment” or “the embodiment” means that a particular feature, structure, or characteristic described in connection with that embodiment is included in at least one embodiment. Thus, the quoted phrases, or variations thereof, as recited throughout this specification are not necessarily all referring to the same embodiment.

As the following claims reflect, inventive aspects lie in a combination of fewer than all features of any single foregoing disclosed embodiment. Thus, the claims following this Detailed Description are hereby expressly incorporated into this Detailed Description, with each claim standing on its own as a separate embodiment. This disclosure includes all permutations of the independent claims with their dependent claims.

Recitation in the claims of the term “first” with respect to a feature or element does not necessarily imply the existence of a second or additional such feature or element. It will be apparent to those having skill in the art that changes may be made to the details of the embodiments described herein without departing from the underlying principles of the present disclosure. 

1. An explosive composition comprising: an explosive comprising ammonium nitrate and fuel oil; and coated urea.
 2. The explosive composition of claim 1, wherein the ratio of the explosive to the coated urea is from about 1:1 to about 3:1.
 3. The explosive composition of claim 1, comprising from about 0.5 weight percent (wt %) to about 30 wt % coated urea.
 4. The explosive composition of claim 1, wherein the coated urea is in the form of prills or granules.
 5. The explosive composition of claim 1, wherein the coated urea comprises a water resistant coating.
 6. The explosive composition of claim 5, wherein the water resistant coating is selected from at least one of a polymer, a wax, a stearate, a silicone polymer, a hydrophobic clay, a hydrophobic silica, a hydrophobic and particulate solid, a dimer acid, and an oligomeric acid.
 7. The explosive composition of claim 5, wherein the water resistant coating is a polymer selected from at least one of polyethylene terephthalate (PET), low-density polyethylene (LDPE), high-density polyethylene (HDPE), low-density polypropylene (LDPP), high-density polypropylene (HDPP), a polyamide, a polyester, polylactic acid, acrylonitrile butadiene styrene (ABS), and polystyrene.
 8. The explosive composition of claim 1, wherein the coated urea comprises unreacted urea.
 9. The explosive composition of claim 1, further comprising an emulsion.
 10. The explosive composition of claim 9, comprising from about 10 wt % to about 60 wt % emulsion.
 11. The explosive composition of claim 1, wherein the explosive composition is water resistant.
 12. The explosive composition of claim 1, wherein the explosive composition is resistant to humid conditions.
 13. The explosive composition of claim 1, wherein the explosive composition is resistant to warm temperatures.
 14. The explosive composition of claim 1, wherein the explosive composition is resistant to liquefaction.
 15. The explosive composition of claim 1, wherein upon detonation of the explosive composition, production of post-blast nitrogen oxide is reduced.
 16. A method of loading a blasthole with an explosive composition, the method comprising: mixing an explosive comprising ammonium nitrate and fuel oil (ANFO) with coated urea to form the explosive composition; and delivering the explosive composition to the blasthole.
 17. The method of claim 16, further comprising adding an emulsion to the explosive composition.
 18. The method of claim 16, further comprising detonating the explosive composition, wherein production of post-blast nitrogen oxide is reduced.
 19. A method of reducing post-blast nitrogen oxide, the method comprising: mixing an explosive comprising ammonium nitrate and fuel oil with coated urea to form an explosive composition; and delivering the explosive composition to a blasthole.
 20. The method of claim 19, further comprising adding an emulsion to the explosive composition. 